High-speed downlink packet access in radio communications system for communications of data over radio links in direction from a radio base station to mobile user equipment is previously known. In high-speed downlink packet access data is generally buffered as need be and transmitted to the receiver at a speed as high as possible considering recent estimates of channel quality. During periods of severely disturbed channels data rate is reduced to zero and no data is transmitted. In this sense the communication is opportunistic.
Prior art example systems where opportunistic communications is incorporated, at least partially, are High Speed Downlink Packet Access (in UMTS), HSDPA, High Data Rate (in CDMA2000), HDR, Selection Diversity Forwarding, SDF, and Multiuser Diversity Forwarding, MDF. Selection Diversity Forwarding is a routing/channel access scheme for an unreliable broadcast oriented medium, selecting a preferable route of forwarding messages depending on outcome of multicasting and e.g. forward progress, cost progress or queue status. MDF is also a routing protocol. SDF and MDF are described in U.S. Patent Application No. 2002/0051425 and U.S. Patent Application No. 60/461839.
In contrast to opportunistic communications conventional radio communications utilize a set of one or more radio channels, the radio communication system adjusting transmission power to the various channels by means of transmission power control striving to achieve (at least) minimum quality requirements. Conventional radio communications have a long-term record of efficiently carrying voice traffic and real-time data traffic. Reliability of conventional data channels may be increased by, e.g., forward error control, FEC, and automatic repeat request, ARQ.
Examples of earlier known channel quality measures are channel signal to noise ratio, SNR, carrier to interference ratio, CIR, received power, received symbol energy, bit error rate, BER, and block error rate, BLER.
U.S. Pat. No. 6,097,703 discloses a multi-hop packet radio communication system utilizing opportunistic peak-mode transmissions to transmit data between originating and destination stations via one or more intermediate stations. Each station monitors the activity of other stations in the network, storing connectivity information for use in subsequent transmissions. Each station also sends out probe signals from time to time, to establish which other stations are in range.
N. Souto, J. C. Silva, A. Correia, F. Cercas, A. Rodrigues: ‘UMTS AWGN Simulation Results for Uplink, Downlink and HSDPA transmissions,’ 2002 describes simulation results in terms of BER (bit error rate) and BLER (block error rate) of HSDPA (High Speed Downlink Packet Access). Downlink rates up to 384 kbps and HSDPA 1600 kbps and 2352 kbps modes were also simulated. For downlink and HSDPA modes, interference is claimed to have no effect in the AWGN channel due to the orthogonal features of spreading codes.
U.S. Patent Application US2002/0141367 discloses a radio communication system implementing both HSDPA and conventional asynchronous communications using different logical channels for control information related to HSDPA and DPDCH (Dedicated Physical Data Channel) respectively.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network, Physical layer aspects of UTRA High Speed Downlink Packet Access (Release 4), 3G TS 25.848 v4.0.0, France, March 2001, describes the physical layer aspects of the techniques behind the concept of high-speed downlink packet access (HSDPA) and includes performance and complexity evaluation of HSDPA. Chapter 6 discusses HSDPA mapping to physical channels.
None of the cited documents above discloses separating or orthogonalizing respective physical traffic channels for opportunistic communications and conventional communications.